Characterization of Microbial Degradation Products of Steviol Glycosides

Steviol glycosides were subjected to bacteria present in a soil sample collected from a Stevia plantation in Paraguay. During the incubation experiments, next to the aglycon steviol, steviol degradation products were also formed. X-ray analysis and NMR methods in combination with chemical synthesis and GIAO NMR calculations were used to fully characterize the structure of these compounds as a tricyclic ketone and the corresponding reduced form. They were nicknamed monicanone and monicanol. The latter has the (S)-configuration at the alcohol site.     

Anionic and pseudoanionic polymerization of lactones - a comparison

Polymerization via anionic mechanisms or insertion mechanisms (pseudoanionic mechanisms) are compared for β-lactones and L-lactide. The following aspects are discussed: initiation and deprotonation of β-lactones, back-biting degradation, stereosequences of poly(β-D,L-butyrolactone), racemization of L-lactide, systematic variation of endgroups including synthesis of macromers.     

Multi-phase modeling of shape memory polymers

In the present work, we propose a model for shape memory polymers based on the idea of the multiplicative decomposition of the deformation gradient. Evolution equations for the several deformation components are presented that provide for the storage of the entropy-elastic strain and its recovery during the transition between the frozen phase and the active phase. First characteristic shape memory cycles for small and large deformations will be shown as a last point. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Polymerization of norbornene with Co(II) complexes

The norbornene polymerization was studied in the presence of 6 pyridine bis(imine) cobalt(II) complexes activated with methylaluminoxane (MAO). Norbornene was also polymerized with CoCl₂ associated to MAO. All these catalytic systems generate an addition polymerization of norbornene, yielding fully saturated polymers. It was shown that the polymerization yield and the molar masses are highly dependant on several reaction parameters (monomer concentration, [Al]/[Co] ratio, polymerization temperature and time) and the frame of the ligand.